1. Field of the Invention
The present invention relates to the field of interfacing peripheral devices to a computer system, and more particularly, to methods and apparatus for bus cycle tracking variable delay lines.
2. Art Background
In order to integrate peripheral components, such as external memory cards, modems and the like, some computer systems comprise an open-ended architecture such that a number of peripheral components may be interfaced to the computer system. Computer systems comprise, address, data and control buses to provide a means for interfacing peripheral components with the computer system resources. In order to interface external peripheral components to a computer system, the computer buses comprise timing and voltage level specifications such that a designer need only comply with the bus specifications to interface the desired peripheral component with the computer system. However, once the bus specification is fixed, it cannot be changed without losing compatibility with existing peripheral components. It may be desirable to change the timing specifications, or AC specifications, because new technology provides faster components. Therefore, it is desirable to be able to change AC specifications for interfacing peripheral components while remaining compatible with existing peripheral components.
In general, the present invention provides a means for generating an output reference signal to interface peripheral components with a computer system. Specifically, the present invention provides methods and apparatus for tracking a bus cycle to delay the output reference signal in accordance with a timing specification. If the timing specification is changed, or if faster components are used to interface the computer system with existing peripheral components, then the output reference signal is delayed accordingly.